Telephone system.



E. a. @www ai A. BALSE TELBPEGNE SYSTEM.

El) SEPT.17,198. RENRWED AUG. 14, l9l.

Payented Aug. 26, 1913.

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A 0 w I l n w N NN o E o 2Q,

UNITED STATES PATENT OFFICE.

ELMER R. CORWIN AND CHARLES A. BALS, OF CHICAGO, ILLINOIS, ASSIGNORS TOCORWINHFELEPHONE MANUFACTURING COMPANY, OF CHICAGO, ILLINOIS, A COR-PORATION 0F ILLINOIS.

TELEPHONE SYSTEM.

Specification of Letters luatent.

Patented Aug. 26,1913.

Application filed September 17, 1908, Serial No. 453,541. Renewed August14, 1911. Serial No. 644,043.

To all whom it may concern:

Be it known that we, ELMER R. CORWIN and CHARLES A. BALS, cit-izensofthe United States of America, residing at Chicago, in the county ofCook and State of Illinois, have invented a new and useful TelephoneSystem, of which the following is a specification, reference being hadto the accompanying drawing, illustrating same.

Our invention relates to telephone systems having automatic callingmechanism and automatic operators-control mechanism.

The principal objects of our invention are,

to provide improved means for automatically calling subscribers whenconnection is made with their lines; to provide improved means forautomatically controlling such calling apparatus; to provide improvedmeans for controlling the operators connection with the various cordcircuits of the system; and to provide other improved circuitarrangements hereinafter described.

The accompanying drawing is a diagrammatic illustration of a pair oftelephone lines extending from substations to a central eX- change, anda connecting circuit for the lilies having the necessary apparatusassociated therewith for operating the system in accordance with thisinvention.

The line of subscriber A extends in two limbs 1 and 2 to suitableconnection terminals 3 and 4, respectively, of a spring jack C at thecentral exchange. Terminals 3 4 normally engage contactsl 5 6,respectively, but are adapted to disengage these contacts when a plug isinserted into the jack. Contact 5 extends through a line lamp T to thelive pole 8 of battery D, the opposite pole 9 of battery D beinggrounded. Contact 6 is connected direct to ground, as is also thethimble 10 of the jack C. At the substation A. limb 2 of the line isnormally7 connected through ringer 11 and a condenser 12 to ground, thisconnection to ground being broken when the. receiver' is removed fromthe switch-hook .13 in the ordinary manner. Substation A also containsthe ordinary talking apparatus. The line of subscriber B is similar toline A and like characters have been used to represent like parts inconnection with the two lines.

In the plug-cord connecting circuit the answering plug l'l and thecalling plug F have their tip contacts 14 14 and ring contacts l5 15connected together, respectively,

through respective condensers 16 1T, these strands through the plug-cordcircuit constituting the metallic talking circuit through the connectingcircuitwhen the connecting plugs E and F are connected with lines. TheplugsE and F have their sleeve contacts 18 18 connected throughrespective windings 19 and 2O of an operators differential relay H topole' 8 of battery D. The windings of this relay are so arranged thatwhen either one of the connecting plugs E F is connected with a line therelay will be energized and will thereby connect the operators telephoneset with the corresponding connecting circuit. the operator`s telephoneset beingv normally disconnected from the connecting `circuit atcontacts 21 22 and 23 24 which are controlled by the relay H, and thebattery circuit of the operators transmitter 25 being normally open atcontact- 26 2T which is also controlled by relay H. The windings ofrelay H are also arranged so that when both of the connecting plugs Eand F are connected with lines the relay H is deneigized.` under theseconditions the windings 19 and 2O of relay H acting differentially.Therefore it will readily be seen that it is inipos sible for theoperator to listen in on a connection established between two lines, andthat the operators set is controlled by a single relay for each pair ofcords before her. J is an impedance coil through which talking batterytrom battery D is supplied to the operators transmitter 25.

The answering supervisory lamp 28 is controlled by contact 29 30 whichis controlled by relay K. This relay Kelso serves as an impedance toboth limbs of the metallic talking circuit. W'hen the calling plug F isconnected with a line, relay L becomes energized and thereby closesnormally open contacts 31 32 and 33 34. These contacts control thecircuits of the ringing generator G and the interrupter M. respectively,as will be hereinafter described. Contact 31 32 is in a limb of thetalking circuit. The interrupter M when operated periodicallyy closesand opens a contact 35 36 which is in the circuit of winding 43 of relayN, so that the interrupter M will control the operation of relay N aswill` be hereinafter described. The calling supervisory lamp 37 iscontrolled by a contact 38 39 which is controlled by relay N. Relay Nalso controls a normally closed contact 40 41 in ythe circuit of ringinggenerator G, and a; normally open contact 41 4Q in a limb of the talkingcircuit. lVinding 44 of relay N is connected from a limb of' theplug-cord talking circuit to pele 8 of battery D, and in addition toenergizing` the relay N as Will be hereinafter described, it serves asan impedance-to this limb of the talking circuit. lVinding 45 of relay Pin addition to energizing relay P as will be hereinafter described, alsoserves as an in'ipedance to one of the limbs of the talking circuit.Relay P controls a normally closed contact 4G 47 in the circuit ofringing generator (l, a normally closed Contact 48 4t) in the circuit ofinterrupter M, a normally closed Contact 50 5l in the circuit of winding43 of relay N, and a normally open Contact 50 .72 in circuit withwinding 53 of relay P. The Contact 50 52 is for the purpose of r:ausingrelay P to lock itself in operated position from the time the circuit ofthe line is closed while the calling plug F is connected therewith.until thev plug F is disconnected from the line, for purposeshereinafter' described. The contacts 14, 15 and 18 of each oftheconnecting plugs ll and F register with conta-cts 3, 4 and 10 of a jackC when connection is made with a line.

The operation of the system is Assuming that subscriber A and conversewith subscriber B, he first removes his telephone receiver from theswitch-hook which closes the circuit of his metallic line through hissubstation and thereby closes a circuit of battery D through line lamp 7belonging to line A, and through the metallic line A back to ground atthe central station. Current from battery D flowing through lamp 7 whichconveys to the operator a signal for connection. The operator then in-/serts the answering plug E into the jack C of line A and by so doingopens jack contacts 3 5 and 4 6 to prevent the line lamp 7 of line Afrom displaying a signal, and closes 'the following circuits: First.From pole 8 ot battery D through winding 19 of relay H and plug-jackcontact 18 10 of line A to ground. Current from battery D flowingthrough this circuit energizes relay H and thereby causes saine to closecontacts 2l 2?. Q3 Q4 and Q6 27, which bridges the iperators telephoneset across the metallic plugeord talking circuit and also Supplies tl eoperators transmitter 25 with battery Vfrom pole 8 ot' battery l)through inuiedance roil J. contact 27 Q6, and transmitter 25 to ground.Second. From pole 8 of battery D through winding 54 of relay K. thrtmghthe metallic line A. and through winding 55 of relay K to ground.Current from battery D tiowing through this circuit energizes relay Kand thereby causes same to open contact 29 30 to prevent the supervisorylamp 28 from displaying a signal. Now the as follows: desires to callthis circuit lights the line l l l l g Vthis circuit starts the operatorconversos with the party at substation A and finds out from him that theparty at substation .B is desired. The operator now inserts the callingplug F into the jack C of line l. which opens jack contacts 3 5 and 4(3, to prevent the line lamp 7 of line B from displaying a signal, andcloses, or causes the closure of, a number of circuits as follows:First. From pole 8 o1 battery D through winding Q0 of relay H, andplug-jack contact 18 l() et' line Il to ground. through this circuitcauses relay ll to be come denergized, because winding# 1f) and 20 ofrelay H now act ditl'erentially, and thereby open contacts 21 22, 23 24and Q6 27, which disconnects the operators set from the plug-cordtalking' circuit and opens the battery circuit through the operatorstransmitter Second. From pole 8 of battery D through calling supervisor;lamp 37, contact 38 39 of relay N, and plug-jack Contact 18 10 of line Bto ground. "Current from battery D flowing through this circuit causessupervisory lamp 37 to display a signal, which indicates to the operatorthat line B is not taken fer use. Third. From pole 8 ot battery Dthrough the winding of relay L, and plug-jack contact 18 10 of line B toground. Current from battery D flowing through this Circuit cnergizesrelay L and causes it to close contacts 31 32 and 33 34. Fourth. Contact31 32 being closed closes a, circuit of rii'iging generator Ur throughcontact 46 47 of relay P. contact 4() 4l 0f relay N, contact 32 31 ofrelay L, plug-jack Contact 15 4, limb 2 of. line B, ringer '11, andcondenser l2 to ground. Current from ringing generator G flowing throughthis cirv cuit operates the ringer 11 at. substation l and therebysignals the party at substation to answer hisl telephone. Fifth.ContactJ 33 34 being closed closes a circuit from pole 8 of battery Dthrough the armature of interrupter M, contact 48 49 of relay P, contact34 33 of relay L, and plugjack Contact 18 10 of line B' to ground.Current from battery D flowing through operation of interrupter M andthereby causes it toperiodically close and. open Contact 35 36,as `willbe readily understood. Sixth. When contact 35 36 is closed it closes acircuit from pole 8 of battery D through contact 35 36 of theinterrupter M, winding 43 of relay N, contact 51 50 of relay P, andplugjaCk..con tact 1S 10 of line B to ground. Current from battery Dflowing through this circuit energizes relay N and causes same to opencontacts 38 39 and 40 41. and elo-se contact 41 42. Contact 38 39 beingopen extinguishes the supervisory lamp 37. Contact 40 41 being openstops the flow of current from ringing generator G over line B. Contact41 42 being closedrcloses a break lurrent from battery D flowing in alimb of the plug-cord talking circuit to complete the continuity ot saidtalking circuit. In a few seconds the continuous operation ot' theinterrnpter M causes contact 35 S6 to again become open, which deenergizes relay N and causes it to open contact 41 l2 and close contacts40 41 and 3S 39. Contact 4() 11 being now closed causes ringing currentfrom ringing generator G to again flow over limb :2 of line B and againring the. ringer at. substation B. Contact 38 39 being now closed againcauses thc supervisory lamp 37 to display a signal. As the operation ofthe interrupter M continues it causes ringing current to be sentperiodically over limb of line B to periodically ring the ringer l1 atsubstation B, and also causes thc supervisory lamp 3T to give a signalperiodically, simultaneously with the ringing of the ringer atsubstation B, in the manner described above. Then the party atsubstation B answers his call he removes his receiver from theswitch-hook in the usual manner, which closes the circuit between thelimbs olf his line and thereby closes a circuit from pole S of battery Dthrough winding 4-1 ot' relay X. contact 12 41 of relay N. contact 3:231 of relay L, plugiack contact l5 4 of line B, the metallic line B,plug-jack contact 3 14 of line B, and winding 45 of relay P to ground,provided intcrrupter M has contact 35 36 closed so as to energize relayX and thus cause the latter to have contact 11 42 closed; this conditionheilig attained as soon as the interrupter M closes contact 35 S6 afterthe party at substation B removes his receiver from the switch-hook. ifthe contact 35 36 is not already closed when the receiver is taken foruse. Current flowing through this circuit gives additional energy torelay N and also energizes relay P and causes the latter to opencontacts 46 4T. 48 4f) and 50 51, and close contact 50 Contact 46 47being open prevents the flow of ringing current from ringing generator Gover line B. Contact 48 49 being open stops the operation ot'interrupter M, provided the interrupter M is not operated by having itsarmature circuit closed by apparatus of other cord circuits. Contact.5051 being open prevents current from flowing through winding 4B of relayN, even if interrupter )l should be still in motion so as toperiodically close contact 36. Contact 50 being closed closes a circuityfrom pole 8 of battery l) through winding 53 of relay P, contact 52 5()of relay P, and plug-jack contact 1S 1() ot' line B to ground. Currentfrom battery D flowing through this circuit keeps relay P energizeduntil the plug F disconnected from the jack C, independcut ot whether acircuit of battery D is closed through winding 45 o relay P or not. N owthe parties at substations A and B are `connected tor conversation witheach other. the talking circuit being continuous through contacts 2:1 32and 4:1 l2 of relays L and N, respectiyely. all ot' the relays exceptrelay H being now energized. When the conversation is completed and theparty at substation hangs his receiver upon the switch-hook he opens thecircuit ot' his metallic line at his substation and thei'cby stops thetlow ot current through supervisory relay K. thus allowing relay K torelease its armature and close contact it 3o. Contact 29 30 being closedcloses a circuit from pole 8 of battery l) through contact 30 answeringsupervisory lamp L) and plug'-y jack contact; 18 l0 of line C to ground.Current from battery D tlowing through this circuit lights thesupervisory lamp which indicates to the operai or that the party atsubstation has tiuished with the use ot' his line. When the party at.substation l hangs his receiver upon the switch-hook he opens thecircuit of his metallic line at his substation and thereby stops theflow of current through winding 15 of relay l and winding il of thecalling siuiervisoiwv rela); N. thus allowing relay N to release itsarmatures and thereby open c ontact il i2 and close contacts 0 41 and 3S39. Contact 38 39 being closed closes a circuit from pole 8 of battery Dthrough calling supervisory lamp 3T, contact 38 39 of relay N, andplug-jack Contact 18 lof line B to ground. Current from battery l)flowing through this circuit lights the supervisory lamp 37. whichindicates to the operator that the party at substation B has finishedwith the use of his line. The operator now withdraws the connectingplugs E and F from their respective spring jacks C C, thereby openingthe circuits of lamps 28 and 3T and extinguishing their signals. Thistlisconnection of the lines also opens the circuits through the windingof relay L and through the winding 53 of relay l). therelrv permittingthe armatures of these relays to release and take their normalpositions. .tu making this disconnection the operator also opens thecircuits through windings 19 and 20 of relay H, thereby stopping theflow of current through these windings 19 and 2b. Now all of thecircuits and apparatus are in their normal position and condition, readyfor other connections to be made for conversation between the lines ofthe system.

Ve do not Wish to limit this invention to all of the particular details,or to the particular pieces 'of apparatus', herein shown. as variousmodifications may be made there- 'in Without departing from the scope ofthe appended claims Vhat We claim as our invention is:

1. The combination in a telephone system having lines, of a connectingcircuit for the,

lines, a source of ringing current, a ringing relay associated with theconnecting cir-l cuit for applying the source of ringing current to a mewhen connection 1s made therewith, a supervisory signal, a supervisoryrelay having switching mechanism controlling 4the circuits of thesourcey of ringing current and the said. supervisoryy signal, aninterrupter controlling a circuit of the supervisory. relay whereby thelatter causes peri- 1c ringing and a periodic operation of the saldsupervisor signal when connection is made with. a ca led line, the saidinterrupter being under control of the ringing relay, a locking relayadapted to be operated when the line with which connection is made istaken for use, and switching mechanism under control of the lockingrelay whereby the latter controls the circuits of the source of ringingcurrent, of the interrupter, of the supervisory relay, and its owncircuit, when the line-is taken for use while connection is madetherewith, whereby said locking relay is locked in operated positionuntil connection is disestablished with the line. The combination with atelephone system having lines, of a connecting circuit for the lines, asource of ringing current, a ringing relay, a supervisory relay, and alocking relay, associated with the connecting circuit and eachhavingswitching mechanlsm controlling the circuit of the source yofringing current, and an interrupter controlling a circuit of thesupervisory relay whereby periodic ringing is produced when connectionis made with a called line, the said ringing relay applying ringingcurrent to the called line when connection is made therewith, and thesaid locking relay preventingthe ringing current from bein after thesame is taken for use while connection is made therewith.

3. .In a telephone system having lines, a connecting circuit for thelines, said connecting circuit having a talking strand therethrough,said talking strand having a section thereof disconnected therefrom, asource of calling current normally connected with said section of thetalking strand, a relay for connecting said section with a line whenconnection is made therewith, a second relay controlling the connectionof said section with said talking strand, and an interrupter controllingSaid second relay whereby the source of calling current is periodicallydisconnected from said section when connection is made with a calledline, to give periodic signaling over the line.

4. The combination with a telephone system having lines, of a connectingcircuit therefor, said connecting circuit having a talking strandtherethrough, a source of calling current normally connected directlywith a section of said talking strand, a relay for continuing thecircuit of said calling Vtem having lines,

applied to the line' source l. means whereby said ringing over a linewhen connection is made therewith, and interrupter means apart from thecircuit of the said source of calling current fer periodicallycontrolling the connection of lsaid calling source with said section ofthe talking strand, substantially as described.

5. The combination with a telephone sysof a connecting circuit therefor,said connecting circuit having a talking strand therethrough, saidtalking strand having a break therein, a source of calling currentnormally connected directly with a section of said talking strand,means` apart from the circuit of the said source ol calling current forperiodically controlling the connection of said source of callingcurrent with said section of the talking strand` and means forpermanently disconnecting' said source of calling current from saidtalking strand and permanently establishing the continuity of saidtalking strand when the called line is taken for use while connection ismade therewith.

6. In a telephone system having lilies. a connecting circuit for thelines, said connecting circuit having a talking strand therethrough, abreak in said talking strand,- a source of wave form ringing currentnormally connected directly with a section of said talking strand bynon-conductive connections, and means apart from the ringing circuit fordisconnecting said source of calling current from said talking strandand establishing the continuity of said talking strand when the calledline is taken for use while connection is made therewith.

7. The combination in a telephone system having lines, of a connectingcircuit for the lines, said connecting circuit having a talking strandtherethrough, said talking strand having a break therein, a source ofcalling current normally connected directly with a portion of saidtalking strand, means apart from the circuit of the said source ofcalling current for causing periodic signaling from Said source ofcalling current over a called line when connection is made therewith,and means for disconnecting said source of calling current from saidtalking strand and establishing the continuity of said talking strandwhen the called line is taken for use while connection is madetherewith.

8. The combination with a telephone system having lines, of a connectingcircuit for the lines, said connecting circuit having a metallic talkingcircuit therethrough and a third strand, a source of ringing currentnormally connected with a portion of the said metallic talking circuit,a ringing relay for applying ringing current over a called line whenconnection is made therewith, said ringing relay being connected withsaid third strand and being operated when connection is made with aline, an interrupter, relay controls imacat the circuit of saidinterrupter, a supervisory relay controlling the circuit of said sourceof ringing current and a portion ot the said metallic talking circuit, asupervisory signal underontrol of said supervisory relay, means wherebythe said interrupter controls a circuit of the said supervisory relaywhereby the latter causes periodic ringing over a called line whenconnection is madetherewith, and simultaneous periodic operation of saidsupervisory signal, a locking relay controlling aA circuitI of its own,the circuit ot the said source of ringing current, the circuit of thesaid interrupter, and 'the said circuit of thesupervisory relay, saidsupervisory relay and said locking relay haring respective windingswhich serve as impedances for the respective limbs of said talkingcircuit and whereby the said relays are energized when the line withwhich connection is made is taken for use, the said supervisory relaythen disconnecting a portion of the ringing circuit from the saidtalking circuit and establishing the continuity of the talking circuit,and also rendering the said supervisory signal inoperative, the saidlocking relay then rendering the said source of ringing current and thesaid interrupter inoperative, provided they are not operated throughother similar connecting circuits, said locking relay keeping itself inoperated position until connection is disestablished with the line, andsaid supervisory relay becoming dencrgized upon the discontinuance ofthe use of the line with which connection is made, whereby thesupervisory signal is operated.

9. ln a telephone system having lines, a connecting Acircuit for thelines, said convnecting circuit havingr a talking strand therethrough, asource of calling current norinaily connected directly with at least aportion of said talking strand, means apart from the circuitof the saidsource of caliing'current, for producing periodic ringing over saidtalking strand and a line when connection is made therewith, and alocking relay opening the circuit of the said source of calling currentwhen the line is taken for use while connection is made therewith, saidlocking relay then closing a circuit of its own whereby it is heldinoperated posit-ion until connection is disestablished with the line.

10. In a telephone system having lines, a connecting circuit for thelines` said connecting circuit having a talking strand therethrough,said talking strand being normally divided into sections, a source of-calling current normally connected with a section of said talkingstrand, a relay for applying calling current to a line when connectionis made therewith, means for proiucing periodic ringing over saidtalking atrand and the kine when connection is made' is held in operatedposition until connection is dis-established with the line.

1ll In a telephone System having lines,

the combination of a connecting circuit forthe lines, said connectingcircuit terminating in a pair of connecting plugs, an operatorstelephone set normally disconnected from the connecting circuit, saidtelephone set having a transmitter the battery circuit of which isnormally open, and a differential relay controliing the connection ofthe operator-s set with the connecting circuit and the battery circuitthrough the operators transmitter, said relay having a pair of windingsconnected with the respective connecting plugs, whereby the connectionof either one of the said connecting plugs with a line connects theoperators telephone .setwith the connecting circuit for conversationalpurposes, and whereby the connection of both of the said connectingplugs with the lines causes the operator`s telephone set to bedisconnected from the connecting circuit and the operators transmitterbattery circuit to be opened.

12. telephone exchange system including telephone lines extending to anexchar'ige` connecting apparatus for uniting. lines in conversation,operators telephonie apparatus including a telephonie transmitter, asource of current for supplying said transmitter with operating current,and

mechanism governed by the connecting ap- 'zoV 14. A telephone exchangesystem including telephone lines extending to an exchange, connectingapparatus for uniting lines in conversation, operators telephoneapparatus, and electro-magnetic mechanism for automatically controllingrthe association of.

said apparatus with said connecting apparatus and for controlling theapplication of current to the operators transmitter by way of theconnecting apparatus.

15.'A telephone exchange system including telephone lines extending toan exchange,

connecting' apparatus for unit-ing' lines in ctnwersalion, operatorstele '1 including' a teler' of current for supplying' sali withoperating current,` and nu' erned by the connecting' appara trollingrthe application ot' current erators transmitter' by Way of the inn'apparatus.

1G. A telephone exchange system harina' a common battery and includingtelephone lines extending to an exchange, connecting apparatus foruniting' lines in conversation, operators telephone apparatus in:- :dinga telephone transmitter in circuit connection with the common battery, asource of current for supplying' said transmitter with operatingcurrent, and electro-magnetic :riechanisin lgoverned by the connectingapparatus for controlling' the application of current to the operatorstransmitter.

17. A telephone exchange system including' telephone lines extending toan exchange, operators telephone apparatus, and electromagneticmechanism whose operation is effectedwhen said connecting apparatus isunited With a calling line for the purpose of associating' the operatorstelephone outfit. with the callingA line and supplying' the operatorstransmitter with operatingcurrent, and which electro-magnetic mechanismis released Iwhen the connecting apparatus is united with a called line,thereby to exclude the operators telephone set from circuit.

ismit-ter .f.= the opconnect- 18. A telephone exchange system including'telephone lines extendingr to an exchange, operators telephoneapparatus, and electromagnetic mechanism for including,r the operatorstelephone set in circuit and supplying the transmit-ter thereof withoperating current, said mechanism including' an electro magnet haring`differentially Wound coils, the circuit through one of lWhich bein,"Tcontrolled by the connecting apparatus and apparatus associated With thecalling line and the circuitthrough the other ofavliich beine;controlled by the connecting apparatus and apparatus associated with thecalled line.

19. A telephone exchange system including telephone lines extending' toan exchange,

q l operators telephone apparatus, and electromagnetic mechanism forincluding the operators telephone set in circuit and supplying' thetransmitter thereof Withl operating current, said mechanism including"an electro-magnet having' differentially Wound coils, the answerinaf'endof the connecting' apparatus entering' into the control of one I' coiland the connecting end of the connecting apparatus entering into thecontrol of the other coil.

Q0. A telephone exchange system including telephone lines extending' toan exchange, operators telephone apparatus, and electrosaidineciroperators tel map'rn'ltic mechanism for supplyinf" i oratore trfilth ogo'" havin;`J` diiierentufir 'si' cc" cuit through one oi' whichteine' by the connectii raratuand params associated with il? wilma' liucand the circuit through thel other of which being' controlled by theccnnectine apparatus' and apparatus associated with the called line.

Qi. A telephone exchange system including' telephone lines extending' toan c 'hanx'e,

eohone apparatus, and electroi'najgnetic mechanism for suppl; l j thetransmitter thereof 'with og'feratine' current. said mechanismincluding' an ele' havin-r ditllerential-ly wound ci swerii end oi theconnecting' apparatus cntering into the control of one coil and theconnecting end of the connecting apparatus entering into the control ofthe other coil.

A telephone system including telephone linw extending' to an exchanget'roin sub-stations, jack switches Yin association with the telephonelilies, connecting plugs for engagement with said switches. a source otsignaling current-tor operating' the signal receivers a. calledsub-stations. a relay pci'- niitting the separation of each connecting'plugtrom the source ot ruling current, switching mechanism gnu'cincd bythe associate connecting plug for operating said relay to connect theplug' with the source of ringing current, and thereby to traiisinit theringing' current to the called station, a sccond relay serving', wheninertgto permit ot the connection of the signaling' current with theconnecting plug by the switching' mecha# nism controlled by the firstaforesaid relay and adapted to hare circuit closed therethrough by theswitching; mechanism at the called sub-station when the signal isyresponded to tliereat. :in/l thereby to remore the signaling currentVtrom the called line, athird relay haringA z-zuitchinar mechanismserving, when unattracted, to dissociate the signaling' current from thecalling line and to permit of the passage of such current to the calledline, and an interruptor included in circuit with said last relay,whereby naling currentis intermittently applied to the called line, thesecond relay, when encrp'ized, opening said interrupter circuit.

ccnl rollt'4 93. A telephone system including telephone'lines extendingto an exchange from sub-stations, jack switches inv association with thetelephone lines, connectingr plugs for engagement with said switches. aYsource ot signaling current for operating the signal receivers at calledsub-stations` a relayv `pcr mitting the separation of each connectingplug from the source vof signaling current, switching mechanism`governed by the associate connecting' plug for operating'said relay toconnect'the plug' With the source of rtv-magnet llt) ringing current.and thereby te transmit the ringing current to the called station. a'second relay Serving. when inert. to permit ol' the connection of thesignaling current ivith the connecting plug' by the switching mechanismcontrolled b v the first aforesaid relay and adapted to have circuitclosed therethrough bv the switching mechanism at the called sub-stationwhen the .signal is rcsponded to thereat. and thereby to remove thesignaling current t'rcm the called line.v a third relay having switchingmechanism serving. when unattracted. to dis-ociate the signaling current"from the calling 'line and to permit of the passage ot' such current tothe called line. an interrupter included in circuit vvith said lastrelay. vvherehy -signaling current is intermittently applied to thecalled line. the second relay. when energized. opening said interruptercircuit. and a locl'- ing circuit for the second relay established vvhenit is energized and breakable at the exchange.

Q4. .X telephone system including telephone lines extending to anexchange from sub-stations. jack switches in association with thetelephone lines, connecting plugs for engagement vvith said switches. asource ot signaling current for operating the signal receivers at calledsub-stations. a relay serving` when inert. to permit of the connectionof the signaling current with the connecting plug and adapted to havecircuit closed therethrough by the switching mechanism at the calledsub-station when the signal is respondedI to thereat. and thereby toremove the signaling current from the called line. a second relay havingswitching mechanism serving, when unattracted. to dissociate thesignaling current from the calling' line to permit of the passage ofsuch current to the called line` and an interrupter included in circuitwith said second relay. whereby signaling current is intermittentlyapplied to the called line. the first relay. vvhen energizcd. openingsaid interruptor circuit.

25. A telephone system including telephone lines extending tt, anexchange from sub-stations. jack switches in association with thetelephone lines, connecting plugs for engagement with said switches. asource of signaling current for operating the signal receivers at calledsub-stations, a relay serving, when inert, to permit of the connectionof the signaling current with the connecting plug and adapted to havecircuit closed therethrough by the switching mechanism at the calledsub-station When the signal is responded to t-hereat, and thereby toremove the signaling current from the called line, a second 'relayhaving switching mechanism serving, when unattracted, to dissociate thesignaling current from the calling line and to permit of the passage ofsuch current to the called line, an interrupter included in circuitvvith said second relay. whereby signaling current is intermittentlyvapplied to the called line. the first relay. vvhen energized, opening'said interruptcr circuit. and a lecking circuit for the said relayestablished when it is energized and hreakable at the exchange. j

Q6. A telephone exchange system including telephone lilies extendingfrom Substations to an exchange. a cord circuit uniting lines inconversation, a ringing currentI generator. an electro-magnet for eachcord circuit serving. when inert, to include the source of ringingcurrent in circuit relation ivith the signal bell atthe called `stationand having tvvo circuits, one establishable at the called station whenthe party there responds and the other establishable by saidelectromagnet,` said electro-magnet, when energized. serving to removethe calling gener-a1 tor from circuit relation with the called line.

2T. A telephone exchange system including telephone lines extending fromsub-stations to an exchange. a cord circuit for uniting lilies inconversation, a ringing current generator. an electro-magnet for eachcord circuit serving. when inert. to include the source of ringingcurrent in circuit relation with the signal bell at the called stationand having tvvo circuits. one establishable at the called station whenthe party there responds. and the other establishable by saidelectromagnet, said electro-magnet, when energized, serving to removethe calling generator from circuit relation with the' called line, thecircuits for said electro-magnet including switching mechanism governedby an associate connecting plug.

28. A telephone exchange system including telephone lines extending fromsubstations t-o an exchange, a cord circuit for uniting lines inconversation, a ringing current generator` an electro-magnet for Ieachcord circuit serving, when inert, to include the source of ringingcurrent in circuit relation with the signal bell at the called stationand having tivo circuits. one establishable at the called station whenthe party there responds, and the other establishable "by saidelectro-magnet, said electro-magnet, when energized, serving to removethe calling generator from circuit relation With the called line, thecircuit that is establishable by the electro-'magnet being governed bythe connecting plug, so that it may be opened when the parties arethrough, again to make Said electro-magnet inert to enable the generatorcontrolled thereby again to be included in circuit relation with acalled line.

29. A telephone exchange system including telephone lines extending fromsubstations to an exchange. a cord circuit for uniting lines inconversation, a ringing current generator, an electro-magnet for eachcord circuit serving, when inert, to include the source of ringingcurrent in circuit relation with the signal bell at the called stationand havmg two circuits, one establishable at the called station when theparty there responds, and the other establishable by said electromagnet,said electro-magnet, when energized, serving to remove the callinggenerator from circuit relation with the called line, the circuits forsaid electro-magnet includlng switching .mechanism 'governed by anassociate connecting plug, the circuit that is establishable by theelectro-magnet being governed by the connecting plug, so that it may be'opened when the parties are through again to make said electro-magnetinert to enable the generator controlled thereby again to be included incircuit relation with a called line.

30. A telephone exchange system including telephone lines extending fromsub-stations to an exchange, a link connector uniting lines inconversation, a ringing current generator, an electro-magnet for eachlink connector serving, when inert, to include the Vsource of ringingcurrent in circuit relation with the signal bell at the called stationand having two circuits, one establishable at the called station whenthe party there responds 4and the other establishable by saidelectromagnet, said electro-magnet, when energized, serving to removethe calling generator from circuit relation with the called line. y

31. A telephone exchange system including telephone lines extending fromsub-stations to an exchange, a link connector for uniting lines inconversation, a ringing current generator, an electro-magnet for eachlink connector serving, when inert, to include the source of ringingcurrent in circuit relation with the signal bell at the called .stationand having two circuits, one establishable at the called station whenthe party there responds, and the other establishable by saidelectro-magnet, said electro-magnet, when energized, serving to removethe calling generator from'circuit relation with the called line. thecircuits for said electro-magnet including switching mechanism governedby au associate connecting terminal.

32. A telephone exchange system including telephone lines extending fromsub-stations to an exchange, a link connector for uniting lilies inconversation, a ringing current generator, an electro-magnet for eachlink connector serving, when inert, to include the source of ringingcurrent in circuit relation with the signal'bell at the called stationand having two circuits, one establishable at the called station whenthe -party there responds, and the other establishable by saidelectro-magnet, said electromagnet, when energized, serving to lremovethe calling generator from circuit relation with the called line, thecircuit that is establishable by the electro-magnet being governed bythe connecting terminal, so that it may be opened when the parties arethrough, again to make said electro-magnet inert'to enable the generatorcontrolled thereby again to be included in circuit 'relation with acalled line.

33. A telephone exchange system including telephone lines extending fromsub-stations to an exchange, a link connector for uniting lines inconversation, a ringing current generator, an electro-magnet for eachlink connector serving, when inert, to include the source of ringingcurrent in circuit relation With the signal bell at the called stationand having two circuits, one establishable at the called station when'the party there responds, and the other establishable by Saidelectro-magnet, said electro-magnet, When energized, serving to removethe calling gcnerator from circuit relation with the called line, thecircuits for said electro-magnet including switching mechanism governedby an associate connecting terminal, the circuit that is establishableby the electro-magnet being governed by the connecting terminal, so'thatit may be opened when the parties are through again to' make saidelectromagnet'inert to enable the generator controlled thereby again tobe included in cir- .Cuit relation with a called line.

34. A telephone exchange system including telephone lines extending fromsubstations to an exchange, link circuits for uniting lines inconversation, a source of signaling current, a switch normallyconnecting said source of signaling current with the link circuits, andmechanism for operating said switch to remove the generator from circuitand itself operated by apparatus at the called substation..`

As inventors of the foregoing We hercunto Subscribe our names in thepresence ot two subscribing Witnesses, this l-lth daf/of September,1908.

ELMEH R. CORW'IN. CHARLES A.. BALS. `Witnesses FREDERICK R. PARKER, H.Hor Coon.

